PHOENIX -- As the Arizona Department of Transportation continues to evaluate plans for the proposed South Mountain Freeway connecting the East Valley and the West Valley, the long-awaited draft environment impact statement is ready.

ADOT released the massive document Friday, opening a 90-day period for public review and comment.

The study, which took 12 years and cost about $20.5 million, suggests construction on the South Mountain Freeway go forward.

"The document does recommend that we build something, that regional mobility really requires that we do something here," ADOT spokesman Tim Tait said.

The environmental impact study looked at a variety of factors, including air quality, species disruption, noise pollution and traffic patterns.

The current favored route for the South Mountain Freeway goes down Pecos Road, through the South Mountain Preserve and up 59th Avenue.

"It'll go through about a mile of South Mountain Park, and that is one of the consequences of building this freeway," ADOT spokesman Tim Tait said. "You can't build a freeway without some sort of consequence …."

Going through South Mountain, however, does not sit well with some members of the Gila River Indian Community.

"What matters to me is saving that mountain because many community members consider that mountain sacred," Joseph Perez of the Gila Fiver Indian Community said. "I think everybody agrees they don't want that mountain destroyed."

Last February, the Gila River Indian Community voted down a proposal to build the freeway segment on tribal land rather than through the Ahwatukee foothills.

The South Mountain Freeway concept is by no means new.

Voters first approved funding for the Loop 202 South Mountain Freeway in 1985. Funding for the project also was included in a 2004 proposition passed by Maricopa County voters.

"The South Mountain Freeway is the last piece to complete the Loop 202 and Loop 101 freeway system necessary for high-quality regional mobility, according to the project's engineers," reads the ADOT website.

Carrying a projected 140,000 vehicles per day, the proposed eight-lane, 22-mile stretch of freeway connecting Laveen and Chandler has been the center of debate for years.

The draft environmental document and design concept report is now available for download at azdot.gov/SouthMountainFreeway. It's also available for review at these Valley locations for a 90-day period starting April 26.

The public will be able to provide comments in a variety of ways during the 90-day public comment period, including attending a daylong public hearing on May 21 at the Phoenix Convention Center. Other options are email (projects@azdot.gov), online (azdot.gov/SouthMountainFreeway), via phone (602-712-7006), or by mail to the South Mountain Study Team, 1655 W. Jackson St. MD 126F, Phoenix, AZ 85007.

At the May 21 hearing, which is scheduled for 10 a.m.- 8 p.m., commenters will be limited to three minutes. Members of the public wishing to go over that limit will be able to give their comments to a court reporter or file a written comment form.

Once the final environment impact document is put together -- there is no target date for that right now -- there will be a 60-day period for public review and comment.

If approved, funding to begin construction of the South Mountain Freeway is available as soon as 2015, according to the state's Five-Year Transportation Facilities Construction Program.